f.esson xiv.] ECLIPSES. 67 



observed to move equally with the Sun, and not 

 with the Moon. 



In addition to these circumstances we may 

 observe, that though a solar eclipse may last from 

 beginning to end (at one place on the earth) more 

 than two hours ; yet the duration of total dark- 

 ness can never, in the greatest eclipse he more 

 than four minutes, and very commonly not more 

 than two. 



We may also observe, with regard to eclipses of 

 both luminaries, that in general, as many eclipses 

 happen of the Sun as of the Moon : but in any 

 particular place there are more eclipses of the 

 Moon than of the Sun. Again, that though in 

 lunar eclipses the eastern side is first eclipsed, and 

 the eclipse ends on the western sidej yet in solar 

 eclipses, the western side is first eclipsed, and ends 

 on the eastern. 



As to the number of eclipses both solar and 

 lunar, it may be observed that there cannot in 

 any year be less than two, nor more than seven : 

 the most usual number is four, and it is very sel- 

 dom that there are more than six. 



The satellites of some of the superior planets 

 frequently undergo eclipses and occultations j Hut 

 as these are unobservable by the naked eye, it 

 would not agree with my design to say more 

 about them. Some of the fixed stars, Aldeba- 

 ran for instance, is frequently hidden behind the 

 Moon ; Jupiter also experiences occultations of 

 this kind: but of these the bare mention may- 

 suffice. 



LESSON 



